Formal and informal recovery of recyclables in Mexicali, Mexico: handling alternatives

The purpose of this paper is to review the case of a Mexican municipality in this field and highlight and identify critical gaps to be addressed. The paper seeks to explore intersectorial partnerships as a means to achieve sustainable solid waste management systems. Its point of departure is that, the highest level of service and maximum benefit is gained when a municipality sees its solid waste management mandates and handicaps clearly, uses the strengths of the other actors. The four main types of actors considered in this paper are: the municipal government, the formal private (commercial) sector, and the informal sector, which, includes individuals, small entrepreneurs, and micro-enterprises already working with discarded materials or having the potential to do so. Community based organizations (CBOs), either idealistically motivated or working for their own welfare, and non-governmental organizations (NGOs), usually in pursuit of their own idealistic goals are also a part of the informal sector.     

Environmental cadmium levels increase phytochelatin and glutathione in lettuce grown in a chelator-buffered nutrient solution

Phytochelatins are enzymatically synthesized peptides involved in metal detoxification and have been measured in plants grown at very high Cd concentrations, but few studies have examined the response of plants at lower environmentally relevant Cd concentrations. Using an ethylenediaminetetraacetic acid (EDTA)-buffered nutrient medium, we have varied Cd exposure and measured phytochelatin and glutathione concentrations in romaine lettuce (Lactuca sativa L. var. longifolia Lam. var. Parris Island) grown in a flow-through hydroponic (FTH) system. Very low free ionic Cd (10(-9.6) M) increased average phytochelatin concentrations above those of controls, and increasing Cd resulted in increased phytochelatin production, though increases were tissue dependent. Glutathione concentrations also increased with increasing Cd. In other standard hydroponic experiments, the media were manipulated to vary total Cd concentration while the ionic Cd was fixed. We found that the total amount of Cd (primarily EDTA bound) in the medium altered thiol production in roots, whereas thiols in leaves remained constant. The Cd uptake into roots and translocation to old leaves was also influenced by the total concentration in the medium. Cadmium in all tissues was lower and in some tissues thiol concentrations were higher than in FTH-grown plants grown in identical medium, suggesting that nutrient delivery technique is also an important variable. Though phytochelatin and glutathione production can be sensitive to changes in bioavailable Cd, thiol concentrations will not necessarily reflect the Cd content of the plant tissues.     

Effects of Excess Copper on Growth of Wild Rice (<Emphasis Type="Italic">Zizania palustris</Emphasis>) Seedlings Tested in Reconstituted and Natural Waters

Dissolved copper was toxic to wild rice (Zizania palustris) seedlings when exposed in water from the seed collection site of Swamp Creek, Crandon, Wisconsin, USA, and in laboratory-prepared artificial or reconstituted water. Seeds for the study were harvested, then held through a portion of dormancy, in Swamp Creek. After 60 days they were shipped to a laboratory, chilled, and tested with copper after germination. The end point of the tests was net gain in wet weight of the seedlings; additionally, a pronounced reduction in root development was observed. Using measured concentrations, the lowest no-observable-effect concentration (NOEC) in our study was 37 g/liter in Swamp Creek water and the lowest-observable-effect concentration (LOEC) was 59 g/liter. However, it appeared that there was a point at which concentrations of copper above 400 g/liter did not result in any measurable effect or exhibit a definitive dose–response. Because the results in Swamp Creek water were more relevant to the possibility of local metals additions and the association of reduced seedling growth by copper was more powerful in this water, we derived an equation to express the relationship between copper concentration and toxicity for Swamp Creek water. As an example, we would expect a 3.0% reduction in seedling growth at 5.0 g/liter copper. Seedling roots were particularly affected and the resultant plants may be less well anchored and more susceptible to dislodging than plants not exposed to copper. Further refinement of the methodology may be used to address effects of other contaminants impacting rice beds in North America. This study was conducted while the first author was employed by the U.S. Geological Survey, Mid-continent Ecological Science Center, Fort Collins, Colorado     

Familial marker chromosome due to 3:1 Disjunction of t(9;15) in a grandparent

An extra small chromosome detected in amniotic fluid was identified as the product of a translocation [46,XX,t(9;15)(p24;q11.2)]. This case is unusual in that individuals with the unbalanced karyotype resulting from a 3:1 disjunction are phenotypically normal.     

Digenean trematodes infecting the tropical abalone <Emphasis Type="Italic">Haliotis asinina</Emphasis> have species-specific cercarial emergence patterns that follow daily or semilunar spawning cycles

Approximately 1–2% of the tropical abalone Haliotis asinina inhabiting Heron Island Reef are infected with opecoelid digeneans. These largely inhabit the haemocoel surrounding the cerebral ganglia and digestive gland–gonad complex, and infected abalone typically have significantly reduced or ablated gonads. Observations of infected abalone reveal two distinct cercarial emergence patterns, one which correlates tightly with the abalone’s highly regular and synchronous fortnightly spawning cycle, and the other which occurs in a circadian pattern. The former appears to be a novel emergence strategy not previously observed in digeneans. While the cercariae in all abalone are morphologically indistinguishable, comparison of sequences from the internal transcribed spacer 2 (ITS 2) region of the ribosomal DNA reveals a 5.7% difference between cercariae displaying different emergence patterns, indicating these are two distinct species that probably belong to the same genus. The ITS 2 sequences of the species with the daily emergence pattern are identical to that of an undescribed adult opecoelid from the gut of the barramundi cod, Cromileptes altivelis. Combined molecular, morphological and emergence data suggest that while these opecoelid cercariae use the same first intermediate host and are closely related species—members of the genus Allopodocotyle—they fill different ecological niches that are likely to include different definitive hosts.     

Dispersal decisions and predispersal behavior in <Emphasis Type="Italic">Polistes</Emphasis> paper wasp ‘workers’

Social insects are popular models for studying the evolution of cooperation. Casteless taxa where individuals have the flexibility to either nest alone or cooperate are particularly valuable for understanding the causes and consequences of cooperative behavior. For example, some ‘workers’ from Polistes paper wasp nests disappear from their natal colony soon after pupal emergence and nest independently. However, little is known about dispersal behavior. In this paper, I compare predispersal behavior of wasps who leave their natal colony soon after emergence with behavior of individuals who remain on the natal colony as true workers. I found that P. dominulus females with short nest tenure behave much like gynes (reproductive-destined offspring produced at the end of the season), as wasps with short nest tenure are behaviorally selfish while on the natal colony. They spend a smaller proportion of their time foraging and a larger proportion of their time resting than workers with long nest tenure. In addition, I assessed the factors that may favor early dispersal. Nest environment strongly influenced dispersal; large colonies had a smaller proportion of females with short nest tenure. Queen turnover also increased dispersal behavior perhaps because queen turnover reduces relatedness between a colony’s current and future offspring, thereby reducing the kin-selected benefits of cooperation. Therefore, casteless social insects exhibit a surprising degree of reproductive flexibility. Individuals may use information about their internal state and nest environment to optimize their behavioral strategies.     

Cuckoldry rates in the Molly Miller (<Emphasis Type="Italic">scartella cristata</Emphasis>; blenniidae), a hole-nesting marine fish with alternative reproductive tactics

Microsatellite markers were developed and employed to assess genetic maternity and paternity of embryos in nest-tended clutches of the Molly Miller (Scartella cristata), a marine fish in which alternative reproductive tactics (ARTs) by males were recently described from behavioral and morphological evidence. Genetic data gathered for 1,536 surveyed progeny, from 23 barnacle-nest holes in a single Floridian population, indicate that on average about 5.5 females (range 3–9) contributed to the pool of progeny within a nest. With regard to paternity, the microsatellite data demonstrate that most of the surveyed nests (82.6%) contained at least some embryos that had not been sired by the nest-tending (bourgeois) male, and overall that 12.4% of offspring in the population had been sired via "stolen" fertilizations by other males. These are among the highest values of cuckoldry documented to date in nest-tending fishes, and they support and quantify the notion that the nest-parasitic ART is reproductively quite successful in this species despite what would otherwise seem to be highly defensible nesting sites (the restricted interior space of a barnacle shell). Our estimated cuckoldry rates in this population of the Molly Miller are compared to those previously reported for local populations in other nest-tending fish species, with results discussed in the context of ecological and behavioral variables that may influence relative frequencies of nest parasitism.     

Infrasonic calls of the Asian elephant (Elephas maximus)

Summary Calls at frequencies below the range of human hearing were recorded from two groups of captive Asian elephants (Elephas maximus). Most of the calls ranged in frequency from 14 to 24 Hz, with durations of 10–15 s (Fig. 1). With the nearest elephant 5 m from the microphone, sound pressure levels were 85 to 90 dB (re 20 Pa). These calls occurred in a variety of circumstances. Elephants are the first terrestrial mammals reported to produce infrasound. These calls may be important in the coordination of behavior in thick vegetation or among separated groups of elephants.     

IMPACTS OF A SEVERE SUSTAINED DROUGHT ON COLORADO RWER WATER RESOURCES1

ABSTRACT: The impacts of a severe sustained drought on Colorado River system water resources were investigated by simulating the physical and institutional constraints within the Colorado River Basin and testing the response of the system to different hydrologic scenarios. Simulations using Hydrosphere's Colorado River Model compared a 38-year severe sustained drought derived from 500 years of reconstructed streamflows for the Colorado River basin with a 38-year streamflow trace extracted from the recent historic record. The impacts of the severe drought on streamflows, water allocation, storage, hydropower generation, and salinity were assessed. Estimated deliveries to consumptive uses in the Upper Basin states of Colorado, Utah, Wyoming, New Mexico, and northern Arizona were heavily affected by the severe drought, while the Lower Basin states of California, Nevada, and Arizona suffered only slight shortages. Upper Basin reservoirs and streamflows were also more heavily affected than those in the Lower Basin by the severe drought. System-wide, total hydropower generation was 84 percent less in the drought scenario than in the historical stream-flow scenario. Annual, flow-weighted salinity below Lake Mead exceeded 1200 ppm for six years during the deepest portion of the severe drought. The salinity levels in the historical hydrology scenario never exceeded 1100 ppm.